This invention pertains to hermetic rotary compressors for compressing refrigerant in refrigeration systems such as refrigerators, freezers, air conditioners and the like. In particular, this invention relates to the manner of lubricating the sliding vanes in a rotary compressor.
In general, prior art rotary hermetic compressors comprise a housing in which are positioned a motor and a compressor cylinder. The motor drives a crankshaft having an eccentric portion thereon for revolving inside a bore which is located centrally in the compressor cylinder. The eccentric has a roller rotatably mounted thereon which revolves within the bore as the crankshaft rotates. One or more sliding vanes which are slidably received in slots located in the cylinder wall cooperate with the roller to provide the pumping action for compressing refrigerant within the cylinder bore.
The operating parts of rotary hermetic compressors are machined to extremely close tolerances and the surfaces of the parts are finished to a high degree in order to prevent leakage in the compressor and to provide a very efficient compressor. It is important to properly lubricate the operating parts to preserve the surface finish. Additionally, it is important that proper lubrication be provided for the moving parts of the compressor so that dynamic friction is kept low and frictional losses are minimized. Lastly, by providing adequate lubrication a minimum amount of heat due to friction losses is generated, heat transfer is reduced and the compressor efficiency is improved.
Many types of lubrication arrangements have been provided in the prior art rotary hermetic compressors. Generally, in the prior art arrangements some type of pumping mechanism pumps oil upwardly from an oil sump located in a lower portion of the compressor and distributes the oil to the locations requiring lubrication. The oil is generally slung outwardly to the upper parts of the compressor by means of centrifugal force and is then allowed to drip downwardly by gravity to lubricate the desired portions of the compressor. Excess oil then returns to the oil sump by means of gravity.
Some examples of prior art lubrication arrangements using centrifugal and gravity distribution forces are shown in U.S. Pat. Nos. 3,804,202; 2,623,365; 2,883,101; 2,246,276; and 3,802,937.
One of the problems encountered in prior art hermetic compressor lubrication arrangements has been that insufficient oil reaches the critical areas of the compressor. By relying on the force of gravity or the outward centrifugal slinging of lubricant it is possible that the moving parts in critical areas of the compressor do not receive sufficient oil and are, therefore, not properly lubricated. In particular, the sliding vane surfaces of the compressor should be well lubricated because of the continuous vane loads which minimizes the time for oiling in the vane slot clearances of the compressor cylinder. A more accessible oil supply facilitates lubrication and minimizes vane wear. Furthermore, since both sides of the sliding vane should be well lubricated it is desirable that the lubricating arrangement provides sufficient lubricant to both sides of the sliding vane.
Another problem which has been encountered in prior art compressors is leakage of refrigerant from the high pressure to the low pressure side of the vane. The sliding vane of a rotary compressor divides the low pressure area in the bore of the compressor from the high pressure area in the bore and refrigerant will therefore tend to leak around the sides, top and bottom of the vane from the high pressure side to the low pressure side. Since leakage of compressed refrigerant represents lost work leakage decreases the efficiency of the compressor. It is, therefore, desirable to provide proper lubrication for both sides of the vane to thereby create an oil film on both sides of the compressor vane which forms a hydraulic seal for the sliding vane in the vane slot of the cylinder wall. The oil seal will then block refrigerant leakage around the vane.
Yet another problem which has been encountered in the prior art hermetic rotary compressors is that the lubricant oil is not provided under positive pressure to the areas to be lubricated so that the oil passages for delivering oil to those areas are not always filled with oil. Because of this deficiency it is possible that there will be a lack of adequate lubricant quantities for proper lubrication. It is, therefore, desirable that oil is delivered under positive pressure to the areas to be lubricated so that a sufficient supply of oil is available at all times. It is also desirable that the lubricating oil is delivered under positive pressure so that the oil reaches every portion of the area to be lubricated.